Invicta Men's 1089 Russian Diver Skeleton Watch With Blue Polyurethane Band Case Size : 51.5 mm Dive watch in polished silver tone featuring corrugated bezel, screw-down cap, and skeleton dial with seconds subdial and blue outer dial 52 mm stainless steel case with flame fusion dial window A mechanical watch is a watch that uses a mechanism to measure the passage of time, as opposed to modern quartz watches which function electronically. It is driven by a spring (called a mainspring) which must be wound periodically. Water resistant to 50 m (165 ft): In general, suitable for short periods of recreational swimming, but not diving or snorkeling.